THE  DETERMINATION  OF  SULFUR  IN 
PETROLEUM  OILS 

BY 


GEORGE  ROCKWELL  BARNETT 

B.  S.  Monmouth  College,  1918 


THESIS 

SUBMITTED  IN  PARTIAL  FULFILLMENT  OF  THE  REQUIREMENTS 
FOR  THE  DEGREE  OF  MASTER  OF  SCIENCE  IN  CHEMISTRY 
IN  THE  GRADUATE  SCHOOL  OF  THE  UNIVERSITY 
OF  ILLINOIS,  1922 


URBANA,  ILLINOIS 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/determinationofsOObarn 


\ 


UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 


MAY  31 1 .192  2 


i HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 


SUPERVISION  BY 


GEORGE  RQCEKELL  BARRETT 


ENTITLED  THE  DETSRMIRATIOR  OP  SULPUR  IR  PETROLEUM  OILS— 


BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 


THE  DEGREE  OF MASTER  OP  SGIEROE 

ceS 


In  Charge  of  Thesis 


art.  tTK  cr  Head  of  Department 


Recommendation  concurred  in* 


Committee 


on 


Final  Examination' 


‘Required  for  doctor’s  degree  but  not  for  master’s 


(I) 


TABLE  OF  CONTENTS 


ACKNOWLEDGMENT 

I INTRODUCTION 

II  FORMS  OF  SULFUR 

III  METHODS  FOR  SULFUR  ANALYSIS 

IV  REVIEW  OF  METHODS 

V OEJECT  OF  INVESTIGATION 

VI  EXPERIMENTAL 

VII  MISCELLANEOUS  POINTS 
TAELES 

VIII  SUMMARY  AND  CONCLUSIONS 

IX  BIBLIOGRAPHY 


page  2 

FF*  2-4 
FP.  4-5 
pp.  5-9 
pp.  9-17 
p . 17 

pp.  17-38 
U*  28-40 
p p . 4 1-44 
pp.  45“ 46 


(2) 


ACKNOWLEDGMENT 


The  writer  wishes  to  express  hi  s sincere  apprec- 
iation to  Prof.  S.  W.  Parr.  Much  of  the  present 
work  would  have  been  discouraging  had  it  not  been 
for  the  inspiration  of  his  real  interest  and  wise 
guidance,  which  were  ever  available  to  the  worker. 
The  writer  is  also  grateful  to  Dr.  T.  E.  Layng, 
whose  problem  of  sulfur  removal  was  the  starting 
point  for  the  present  work.  Acknowledgment  is 
likewise  due  the  Standard  Oil  Company  of  Whiting, 
Indiana,  and  the  Texas  Company  of  Houston,  Texas, 
for  complimentary  samples  of  Louisiana  and 
Mexican  crude  oils. 


(3) 

THE  DETERMINATION  OF  SULFUR  IN  PETROLEUM  OILS, 

I INTRODUCTION 

The  problem  ox  determining  the  total  sulfur  content  of 
petroleum  oils  confronted  the  writer  in  connection  with  an 
investigation  of  the  efficiency  of  various  metallic  oxides 
in  removing  the  sulfur.  A lar^e  number  of  sulfur  determina- 
tions were  to  be  made,  and  for  this  reason  a method  was  sougnt 
which  would  d 0 a i mp  1 a 00  c ^ u 1.0  x ana  r a p x. u , a c c i 1 as  accurate, 
ana  a x t n e same  t i m a ap  1 i a a u r e to  ^ ^ li  c u.^-.  0 x w * a a 1 y v a x*y  i ng 
percents  of  sulfur. 

A search  through  the  literature  would  convince  one,  at 
first,  that  it  only  remains  for  the  chemist  to  pick  at  random 
any  one  of  a large  number  Oi  methous  waich  nava,  seemingly , 
been  t r i e a.  out  ■<  1 i:i  success  j v ax  x 0 us  workers,  , - - - u 1 s e 
each  is  seen  to  nave  his  preference,  but  it  is  apparantly 
only  a problem  0 a m a k i ng  a 1 i a l Ox  t a e m e t xx 0 ds  wn  1 c n * xx  e app- 
aratus available  to  the  particular  laboratory  will  permit,  and 
making  the  individual  selection  according  to  the  temperment 
of  the  individual  worker, 

1 1 xx  a a 0 e a ti  w Xi  e exw^-axxenae  ox  0 h e w x x 1 0 x , xx  o w e v e x , L xx  a x 
most  metnods  prove  to  be  disappointing.  Althougn  with  practice 
one  oan  0 b a x n good  o xxe oka  wr  ^ xx  c* pxooeuuxe,  0 xx e oonxidence 
t e mp  or  ax  xij  plaoeu  x n txxe  p x 0 c e a a i a uiaai gated  •. xx  a n o xx  e x c a u 1 1 s 
w a s xx  one  m etxxod  a x a 00  m p a x a a i on  x e s u 1 1 s on  0 n a a a m e o x i 


(4) 

obtained  by  other  methods. 

Although  all  me  o ho  u s were  not  ti  i & uf  tne  ^ e n o x* ax  experience 
uas  been  the  same.  First  comes  the  straggle  to  master  the  re- 
tails oi  the  metnod  (in  general  involving  more  or  less  teuxous 
procedure)  to  make  eacu  step  in  tne  process  exactly  tne  same 
in  all  cases  in  order  to  obtain  good  checks.  Only  to  find  in 
the  end  that  the  pursuit  ol  check  results  nas  indeed  been  but 
the  pursuit  ox  a mirage,  wne n it  is  seen  tha ♦.  another  metnoo 
which  gives  ecpuali^  ^ood  ciiecks  does  not  give  the  same  results. 

It  follows,  then,  that  check*  results  mean  little;  that  the 
same  oil  will  analyze  d i x X e r e n 1 1 y n 1 u a dixici'Siii/  m e t n o d x ; a n u. 
that  tiie  more  me^non***  u s e x i t *.  determining  i iiC  p e r ■ a ^ o x wUli'ui 
in  a certain  oil,  tne  great  . me's  doubt  as  to  now 
sulfur  it  contains. 

In  \ 1 & it  Ox  t n e s e c o n x i a e x e t x o n x , xt  > » cl  s v i 16  d t o x o.  ^ t n x 
main  p r o b i e m ox  tne  removal  Ox  suliux  t e mg o r a x i 1 y upon  tne  x n e 1 x , 
until  the  matter  of  a satisfactory  method  for  the  determination 
of  sulfur  could  be  v/orked  out. 

II  FORMS  OF  SULFUR  PRESENT. 

Unfortunately  xOi  t n e analyst  one  s u 1 x u r in  gecioxeum  uoes 
not  occur  in  one  xox*m  alone,  x u t in  a vai'xety  Ox  f o r m s . In  x p i x e 
of  the  well-known  difficulty  of  isolating  pure  substances  from 
sucii  complex  mixtures  as  petroleum  and  its  fractions,  a large- 
number  have  been  identified.  V.'hen  the  latter  are  classified  it 
is  seen  that  the  sulfur  in  petroleum  is  present  not  only  in 
various  types  of  organic  molecules,  but  as  free  sulfur1,  and 


. 


(5) 

sometimes  as  inorganic  sulfates  if  the  oil  contains  ground 
water  emulsoids  or  inorganic  solids  in  suspension2. 

For  analytical  considerations,  it  is  well  to  keep  in  minu 
the  forms  in  which  the  sulfur  is  present.  For  purposes  of 
tabulation,  the  following  are  named:  (a)  free  sulfur1; 

(b)  hydrogen  sulfide2;  (c)  thiophenes4  and  thiophanes*; 

(d)  alkyl  sulfides6;  (e)  mercaptans7;  (f)  carbon  bisulfide8; 

(g)  sulfonic  acids9;  (h)  sulfonates'0;  and  (i)  alkyl  sulfates1'. 
Inorganic  sulfates  mentioned  in  the  previous  paragraph  are  not 
usually  considered  in  sulfui  analysis,  because  water  and  solids 
are  supposedly  separated  previous  to  the  sampling. 

Ill  METHODS  FOR  SULFUR  ANALYSIS. 

It  is  seen  that  it  is  quite  a problem  to  choose  a combination 
of  procedure  and  reagents  that  snail  be  efficient  in  converting 
all  of  the  sulfur  in  its  various  forms  to  one  certain  form,  and 
separate  it  from  the  other  substances  present  without  loss  of 
sulfur  at  any  point  in  the  process.  The  fact  that  results  by 
different  methods  disagree  among  themselves  makes  it  self-evident 
that  all  of  them  are  not  efficient,  as  they  should  be,  at  least 
in  the  way  they  are  applies.  To  the  present  there  seems  to  be  no 
one  method  which  is  applicable  in  all  cases.  Some  of  them  seem 
altogether  inapplicable.  At  the  most,  it  seems  that  every  method 
proposed  is  subject  to  special  and  often  serious  limitations. 

The  problem  in  sulfur  analysis  is,  then,  to  find  out  which 
of  the  proposed  methods  give  trustworthy  results;  and,  if 


, 


(6) 


possible,  to  find  a new  method  or  improve  one  of  the  old  so 
that  it  shall  be  more  generally  applicable. 

For  future  consideration  it  might  be  well,  at  this  point, 
to  review  the  possible  methods  which  have  been  proposed  for  the 
determination  of  sulfur  in  petroleum  oils  or  similar  substances. 
They  divide  themselves  into  two  main  classes: 

[1]  Reduction  to  Hydrogen  Sulfide. 

The  possibility  of  reducing  all  the  sulfur  to  H2S  is 
interesting  because  tne  latter  is  easily  and  quickly  estimated. 
The  first  attempt  in  this  direction,  as  far  as  known,  was  that 
of  Goetz!'2,  in  which  he  tried  to  fAUge  tne  a... cunt  of  sulfur  by 
the  amount  of  H2S  which  came  off  wuen  tne  oil  was  uis tilled. 
Although  it  is  known  that  oils  containing  no  H2S  originally 
will  evolve  the  gas  when  distilled13,  no  usable  relation  between 
the  amount'  of  sulfur  present  and  the  amount  of  H23  evolved  could 
be  found.  Next  Waters14  attempted  to  hydrogenate  an  engine  oil 
with  gaseous  H2  in  the  presence  of  a catalyzer,  oxidize  the  H2S 
in  an  absorption  solution  of  hypobromite,  and  precipitate  the 
sulfur  as  BaSCU.  Catalyzers  tried  were  metallic  nickel  and  nickel 
oxide,  ana  platinum  foil.  Waters  recovered  only  a very  small 
fraction  of  the  total  sulfur  in  this  way. 

The  most  promising  attempt  yet  made  seems  to  be  that  of 
Heulen15,  by  which  he  heats  the  substance  in  a combustion  tube 
in  a current  of  H2,  passes  the  gases  formed  through  a platinized 
asbestos  catalyzer,  and  absorbs  the  H2S  in  the  effluents  either 
in  alkali  and  determines  it  iodome tricaily,  or  absorbs  it  in 


(7) 

sodium  plumbite  solution,  and  determines  it  colorimetrically. 
Meulen  gives  a table  of  comparative  results  on  seven  different 
petroleum  fractions  and  two  crudes,  ranging  from  .024^-5.  100^  S, 
in  which  he  compares  the  percents  of  sulfur  obtained  gravimet- 
rically  (method  not  stated)  and  obtained  by  his  method.  The 
results  in  each  case  check  remarkably  well  in  every  case,  being 
in  some  instances  lower  and  in  others  higher  than  the  gravimetric, 
but  on  the  whole  slightly  higher.  It  would  be  interesting  to 
know  what  gravimetric  method  he  used  for  comparison. 

Meulen1 s method  is  extreme  Ly  interesting,  because  he  applies 
it  equally  well  on  any  petroleum  or  fraction  oi  high  or  low  sul- 
fur content  (and  on  other  organic  substances,  such  as  coal) . Put 
in  the  opinion  of  the  writer  it  is  not,  at  present,  to  be  viewed 
with  undue  optimism  from  the  practical  analytical  standpoint.  His 
samples  (50  mg.)  are  too  small  to  give  good  checks  on  any  but  the 
most  sensitive  balances,  and  with  larger  samples  it  would  be  ex- 
pected that  trouble  would  be  had  with  rapid  poisoning  of  the  cat- 
alyzer, which  was  probably  Waters  trouble.  In  any  event  it  is  too 
early  to  state  just  what  possibilities  may  lie  in  this  method 
until  it  is  further  tried  in  other  laboratories.  No  work  has  been 
done  on  this  method  in  the  present  investigation. 

[2]  Oxidation  to  Sulfate. 

To  the  second  general  class  belong  ail  of  the  so-called 
standard  anu  rapid  methods*  Ail  of  them  depend  upon  oxidizing 
the  sulfur  to  sulfate,  eliminating  the  residual  oil  (usually  by 
complete  oxidation),  and  determining  the  SC4”.  For  convenience, 

— • > ' ■ - - 


■ 


(8) 

the  methods  have  been  outlined  as  follows: 

1-  Digestion  With  Wet  Oxidizing  Agents. 

(a)  Strong  KMn04-  Waters16. 

(b)  Nitric  or  fuming  nitric  acid-  Waters'7;  Andrews'8; 

Francis  and  Crawford'9;  Calvert20. 

(c)  Nitric  or  fuming  nitric  acid,  and  oxidizing  agents- 

Waters21;  Gilpin  and  Schneeberger2 2;  Francis  and 
Crawford'9;  Gill  and  Grindley23. 

(d)  Hydrogen  peroxide-  Lecocq  and  Vandervoort24. 

(e)  Eoil  NaCH  + Zn+*  + Pb + + to  form  PbS-  Schulz25. 

2-  Burning  Methods. 

(a)  Lamp-  Heusier26;  Engler27;  Friedlander28;  Magruder29; 

Ellerton30;  Conradson31;  Lomax32;  Esling33;  Bordas34; 
Bowman85;  U.  S.  Bureau  of  Mines36. 

(b)  In  enclosed  atmosphere  of  oxygen-  Hempel37;  Grafe38; 

Marcusson  and  Doscher39;  Hauser40. 

(c)  In  combustion  tube-  Mabery41;  Barlow  and  Tolleus42; 

Bay43;  Sauer44;  Dammer44;  Dennstedt46;  Brunck46; 
Vita47;  Lant  and  Lant-Ekl48 . 

3-  Open  Fusion  Methods. 

(a)  With  alkalis-  Eschka49;  Hundeshagen~° ; Handy51;  Heath82; 

Hertig53;  Sadtler~4;  Garrett  and  Lomax55;  Parr66. 

(b)  With  mixtures  of  alkalis  and  oxidizing  agents-  Aufrecht57; 

Lidow58;  Peckham°9;  Langmuir60;  Dubois61; 
Schillbach62;  Blair63;  Chari tschkoff 64 ; Koch  and 
Upson65;  Schreiber66;  Smith67;  Falciola68. 


(9) 


4-  Bomb  Methods. 

(a)  Oxidation  with  fuming  nitric  acid  in  a sealed  tube  under 

pressure-  Carius69  70;  Anelli71;  noland72, 

(b)  Oxygen  Bomb-  Filiti73;  Allen74;  Lord7**;  Lohmann76; 

Philip77;  Falciola78;  U.  S.  Bureau  of  Mines79; 
Christie  and  Bisson80;  Parr8'. 

(c)  Sodium  peroxide-  Osborne82;  Konek83;  Parr,  Wheeler,  and 

Eerolzheimer 84 ; St.  Warunis85;  Lidow-Holde8 6; 

Francis  and  Crawford87;  Franks88;  Parr89, 

5-  Combination  Methods. 

(a)  Wet  digestion  followed  by  dry  fusion  with  alkalis- 

Goetzl90;  Sanders91;  Whittum92;  Rothe93  94  95  96; 
Waters97;  Otsubo98. 

IV  R'EVIEW  OF  METHODS. 

In  reviewing  the  oxidation  methods  under  [2]  , a strict 
historical  presentation  will  not  be  attempted.  The  modifications 
will  be  taken  up  in  the  same  order  as  the  classification  given 
in  the  outline. 

In  the  wet  digestion  methods.  Waters  obtained  low  results 
when  he  attempted  to  oxidize  the  sulfur  with  strong  KMn04  solution. 
He  also  obtained  low  results  with  the  nitric  acid  digestion,  even 
when  adding  such  oxidizing  agents  as  KCIC3  and  KMn04.  Francis  and 
Crawford  came  to  the  same  conclusion  regarding  nitric  acid  diges- 
tion, with  or  without  oxidizing  agents,  even  though  the  digestion 
is  carried  out  under  a reflux  condenser  to  prevent  loss  of  sulfur. 
Andrews,  however,  claims  good  results  when  the  reflux  is  used. 


(10) 

Gilpin  and  Schneeberger  claim  this  method  checks  very  well  with 
the  method  of  Carius,  which  will  be  mentioned  later.  Gill  and 
Grindley  vary  this  method  by  using  KN03  as  the  auxiliary  oxidiz- 
ing agent.  Lecocq  and  Vandervoort  attempt  to  oxidize  with  H2O2. 
Still  another  variation  of  the  wet  method  is  that  of  Schulz,  in 
which  he  boils  the  sample  in  a strongly  alkaline  solution  of 
Zn(C2H302)2  and  Pb(C2H3C2)2»  to  change  the  sulfur  to  PbS,  filters, 
and  fuses  the  residue  with  sodium  and  potassium  carbonates.  Inas- 
much as  the  workers  who  have  tried  these  methods  are  not  agreed 
among  themselves  as  to  whether  the  results  are  to  be  trusted,  it 
is  thought  doubtful  if  much  confidence  is  to  be  placed  in  such 
style  of  attack. 

Of  the  burning  methods,  by  far  the  greatest  amount  of  work 
has  been  done  on  the  lamp  method,  and  its  modifications.  This 
method  adapts  itself  most  readily  to  light  burning  fractions 
containing  a very  small  percent  of  sulfur,  on  account  of  the  fact 
that  a much  larger  sample  can  be  used  than  can  be  taken  by  other 
methods.  The  method  simply  consists  in  burning  the  oil  itself  (or 
mixed  with  a suitr'  i •:  , . h ;,m  11  , solvent)  in  a lamp,  catching 
the  gases  of  combustion  and  passing  them  into  an  absorbing  alkali. 
The  apparatus  needed  can  be  improvised  easily,  but  the  method  is 
objected  to  because  it  is  long  and  tedious,  and  subject  to  error 
because  of  the  retention  of  sulfur  in  the  wick.  However,  if  the 
lamp  method  is  to  be  used,  the  latter  objection  can  be  overcome 
by  running  a sulfur  analysis  on  the  wick,  according  to  Conradson. 
Or  as  suggested  by  Bordas,  a bundle  of  capillaries  can  be  used 
instead  of  a wick.  On  the  whole,  the  lamp  method  is  to  be  avoided 


• 

(M) 

on  account  of  the  labor  involved,  except  in  cases  of  burning 
oils  which  have  so  little  sulfur  as  to  require  a larger  sample 
than  can  be  taken  in  the  oxygen  bomb.  For  these  fractions,  the 
lamp  method  is  considered  the  standard  by  the  U.  S.  Bureau  of 
Mines,  and  others,  and  is  frequently  used  as  a basis  for  reference. 

Burning  the  sample  in  an  enclosed  atmosphere  of  oxygen  is 
used  by  some  workers.  It  consists  of  suspending  the  sample  in  a 
small  container  suspended  in  a large  bottle  (!C-I£  liters  capac- 
ity) filled  with  oxygen.  After  the  combustion  an  absorbing  liqu- 
id is  introduced.  The  metnod  seems  to  have  little  to  recommend  it 
in  the  way  of  convenience  of  manipulation,  and  in  addition  incom- 
plete combustions  are  troublesome.  Burning  the  sample  in  a com- 
bustion tube  in  a stream  of  oxygen  likewise  has  nothing  in  the 
way  of  simplicity  of  operation  to  recommend  it.  The  method  re- 
quires the  usual  combustion  Lrain,  a platinized  asoestos  cat&j.^ - 
aer  to  insure  complete  oxidation,  and  the  reaction  has  to  be 
kept  down  by  a careful  dilution  of  the  entering  oxygen  fc;>  means 
of  carbon  dioxide.  When  properly  controlled  in  every  det  ail  t n e 
method  is  accurate,  but  as  a practical  analytical  procedure  it 
is  to  be  studiously  avoided. 

From  the  standpoint  of  simplicity  of  operation,  fusing  the 
sample  in  an  open  dish  with  alkalis,  or  a mixture  of  alkalis  and 
oxidizing  agents,  would  seem  to  be  the  choice  procedure.  The 
object  is  to  catch  the  sulfur  from  the  decomposing  oil  by  means 
of  the  alkali  present  in  intimate  contact,  completely  oxidize 
the  residual  organic  matter  by  open  ignition,  and  precipitate 
the  sulfur  from  a solution  of  the  residue  as  BaSC4.  The  method 


• t 

. 


(12) 

was  first  worked  out  by  Eschka,  and  although  more  often  applied 
to  coal,  has  been  used  by  some  workers  as  a basis  of  reference 
for  petroleum  oils.  The  reagents  most  commonly  used  are  MgC  and 
Na2C0s  (2:  I),  known  as  Eschka  mixture.  This  is  mixed  with  the  oil, 
sometimes  leaving  a layer  of  the  Eschka  mixture  covering  the  sur- 
face during  the  burning.  Or  a double  crucible  arrangement  can  be 
used,  whereby  the  escaping  gases  are  forced  to  travel  through  2-6 
cm.  of  Eschka  material  before  escaping.  Very  often,  also,  oxidiz- 
ing agents,  such  as  KCIC3,  KNO3,  NH4NO3,  and  I{2Cr2C7  have  been 
used  in  conjunction  with  the  Eschka  mixture,  or  in  special  comb- 
inations without  the  latter.  For  example,  Falciola  mixes  the  sub- 
stance before  ignition  with  KC1C2,  KNCS,  and  NH4N0£  (4: 1:1). 

Smith  uses  precipitated  SiC2,  N a 2 0 2 , and  KClOo.  Schillbach  uses 
Ba02,  treats  with  iTCl,  filters  all  the  soluble  matter,  and  weighs 
the  remainder  as  BaS04. 

A great  deal  of  work  has  been  done  on  these  dry  fusion  methods, 
and  the  Eschka  type  of  procedure  has  enjoyed  a widespread  popular- 
ity. A great  many  writers  seem  to  regard  it  as  a standard,  although 
of  late  there  is  a tendency  to  question  the  accuracy  of  the  results 
with  the  Eschka  method.  Cn  the  one  hand  a worker68  is  congratulat- 
ing himself  because  his  method  checks  so  well  with  Eschka  s,  al- 
though giving  slightly  higher  results;  while  on  the  other  hand  two 
in  conjunction46  condemn  the  Eschka  method,  claiming  that  on  a 
high  sulfur  petroleum  it  gives  2.6%  of  total  sulfur  less  than  the 
actual  sulfur  content.  On  the  whole  the  dry  fusion  method,  with 
or  without  oxidizing  agents,  cannot  be  regarded  with  undue  confi- 
dence at  present.  Part  of  the  present  investigation  has  been  in 


. 


* 


(13) 

this  direction,  and  will  be  covered  further  on. 

Of  the  bomb  methods,  that  of  Carius  was  the  first  orthodox 
procedure,  and  was  intended  for  use  on  any  type  of  organic  sub- 
stance containing  sulfur.  The  procedure  is  to  seal  the  substance 
with  nitric  acid  in  a hard  glass  tube  and  heat  until  oxidized. 

The  SC4~~  is  then  precipitated  with  Ea**,  Roland  includes  KC1C4. 
Anelli  claims  more  satisfactory  results  by  introducing  Ba(N0s)2 
with  the  nitric  acid.  The  Carius  method  doubtless  gives  reliable 
results  on  oils  not  too  low  in  sulfur,  but  only  small  samples  can 
be  taken,  and  if  the  percent  of  sulfur  is  small  the  BaS04  obtained 
is  so  little  as  to  be  difficult  of  satisfactory  manipulation.  The 
method  is  also  objected  to  on  account  of  the  danger  of  the  tubes 
exploding. 

Oxidation  of  the  sample  in  a bomb  under  3C-40  atmospheres 
of  oxygen  is  at  present  generally  regarded  as  the  most  reliable 
method.  About  I gram  of  the  oil  is  placed  in  a small  metal  cru- 
cible inside  the  bomb;  a few  cc’  s of  water  or  alkaline  absorbent 
placed  in  the  bomb;  the  oxygen  introduced  through  a one-way  valve; 
and  the  sample  ignited  electrically.  The  sulfur  is  oxidized  to 
S03  and  unites  with  the  water  forming  S04“' . Careful  analysis  of 
the  residual  gas  has  failed  to  detect  the  smallest  trace  of  incom- 
pletely oxidized  sulfur"  l0°,  when  the  proper  oxygen  pressure 
has  been  provided.  For  oils  not  too  low  in  sulfur,  this  method 
is  the  standard  in  this  country,  as  shown  by  the  fact  that  it  is 
so  regarded  by  the  U..  S.  Bureau  of  Mines  and  the  U.  S.  Bureau  of 
Standards,  in  references  quoted.  It  is  highly  recommended  by  the 
best  writers,  and  the  main  objection  to  it  is  that  the  apparatus 


(14) 

required  is  more  costly  than  the  ordinary  laboratory  can  afford. 

Cutting  down  the  size  of  the  bomb  and  eliminating  the  other 
special  apparatus  required  with  the  oxygen  bomb,  the  sodium  per- 
oxide bomb  has  come  into  favor.  It  is  simple  to  operate,  and  with 
Na202  of  standard  purity  the  results  are  entirely  satisfactory. 
However,  the  allowable  sample  is  only  half  that  of  the  oxygen 
bomb,  so  this  method  is  even  less  adapted  to  low  sulfur  oils  than 
the  former.  The  procedure  consists  in  placing  the  sample  in  the 
bomb  together  with  about  14  grams  of  Na2C2,  and  sometimes  an  ac- 
celerating mixture  of  benzoic  acid  and  potassium  chlorate.  The 
ignition  is  started  by  heating  the  lower  part  of  the  bomb,  after 
which  the  residue  is  dissolved  in  water,  the  solution  acidified 
and  boiled  to  decompose  the  H202>  the  iron  precipitated  by  ammonia 
and  filtered,  and  the  acidified  filtrate  treated  with  BaCl2  to 
precipitate  the  S04~**.  The  article  by  Franks88  is  a good  example 
of  the  careful  application  of  this  method  in  routine  analysis  on 
various  oil  fractions. 

Another  variation  in  the  method  of  attack  is  a combination 
of  wet  digestion,  followed  b>  dry  fusion  with  alkalis.  Sanders, 
Whittum,  Waters,  and  Otsubo  treat  the  oil  at  first  with  nitric 
or  fuming  nitric  acid,  alone,  or  with  an  auxiliary  oxidizing 
agent  such  as  KBr  or  Br2.  The  mixture  is  heated  and  gradually 
brought  to  small  volume,  when  an  alkali  is  added  and  the  organic 
matter  is  driven  off  by  ignition.  In  the  Rothe  method  the  oil  is 
placed  in  a flask  with  MgO,  and  then  a large  excess  of  fuming 
nitric  acid  is  added.  It  is  subjected  to  gentle  neating  for  a 
time,  and  later  ignited  to  decompose  all  the  organic  matter.  In 


' 


’ 


(15) 

all  these  cases  the  residue  is  treated  with  dilute  HC1  and  fil- 
tered, and  the  SO*””  in  the  filtrate  precipitated  with  EaCl2. 

Such  methods  are  usually  applied  to  low  sulfur  oils,  because  from 
5 to  10  grams  of  sample  can  be  taken,  as  compared  with  .5-1.0  gram 
in  the  bomb  methods.  More  will  be  said  later  about  this  type  of 
procedure,  in  connection  with  work  done  in  the  present  investiga- 
tion. 

It  is  seen  from  the  above  that  the  selection  of  a method  for 
determining  sulfur  is  not  always  a simple  one.  The  analyst  must 
take  into  consideration,  in  the  first  place,  the  type  of  oil  to 
be  analyzed.  Next,  he  must  consider  the  accuracy  necessary  to  the 
work  at  hand,  the  number  of  determinations  to  be  made,  the  labor- 
atory equipment  available,  and  so  on. 

The  type  of  oil  to  be  analyzed  has  to  be  considered  because 
there  is  no  method  which  is  perfectly  adapted  to  all  oils.  The 
oxygen  bomb  method  can  be  relied  on  to  give  dependable  results 
with  the  widest  range  of  oils  of  any  other  one  method  (Allen  and 
Robertson  10  ! ) , but  cannot  be  used  on  fractions  of  very  low  sulfur- 
content  because  the  sample  is  limited  to  one  gram.  The  peroxide 
bomb  method  is  very  comparable,  but  the  allowable  sample  is  only 
half  that  of  the  oxygen  bomb.  The  lamp  method  is  adaptable  to 
rather  large  samples,  and  when  the  proper  precautions  are  taken 
gives  dependable  results,  but  even  when  inflammable  solvents  are 
used  it  can  hardly  be  regarded  as  successful  with  heavy  fractions. 
The  Carius  method  is  very  seldom  used  because  it  is  subject  to 
the  same  limitations  as  are  the  bomb  methods,  and  in  addition  has 
objectionable  features  of  its  own.  Of  the  other  methods  or  modifi- 


■ 


( 16) 

cations  cited,  they  are  either  held  to  be  inaccurate,  or  accepted 
with  reservations.  Examples  of  the  latter  class  are  the  Waters 
method  and  the  Rothe  method.  Both  are  combinations  of  the  initial 
wet  oxidation  with  concentration  of  the  sample,  together  with  dry 
ignition  at  the  end.  Any  type  of  oil  can  be  used  (although 
Vandaveer96  applies  the  Rothe  method  to  low  sulfur  oils  only)  and 
relatively  large  samples  can  be  taken.  If  they  give  accurate  re- 
sults, the  methods  would  seem  to  recommend  themselves,  from  the 
standpoint  of  flexibility  at  least.  Waters  claims  good  results 
with  his  method,  and  gives  comparative  results  with  his  method 
and  others  on  the  same  oils.  Good  results  are  also  claimed  for 
the  Rothe  method96.  Investigation  of  the  Rothe  method  formed 
part  of  the  present  work. 

In  considering  accuracy,  e e d which  is  known  to  he  in- 

accurate will  find  very  little  application.  Since  goou  qualita- 
tive methods  are  known19,  in  which  a rough  estimate  of  the  amount 
of  sulfur  can  be  made,  it  is  questionable  whether  an  inaccurate 
quantitative  method  has  any  use  at  ail. 

The  length  of  time  required  to  make  an  individual  determina- 
tion is  an  important  point  to  be  considered,  even  when  only  an 
occasional  analysis  is  run,  and  for  routine  work  the  tediousness 
of  some  methods  is  an  absolute  veto  as  far  as  the}  are  concerned. 
Of  the  more  dependable  methods  the  bomb  methods  are  about  the 
speediest  and  the  lamp  method  the  slowest,  with  the  Waters  and 
Rothe  methods  in  between. 

As  to  the  apparatus  required,  the  oxygen  bomb  method  invol- 
ves the  greatest  outlay,  including  the  tank  of  compressed  oxygen 


. 


(17) 

and  fittings  besides  the  bomb  itself.  The  peroxide  bomb  is  less 
expensive,  but  cannot  be  improvised.  Apparatus  for  the  other 
methods  is  of  the  ordinary  laboratory  type,  or  can  be  improvised. 

V OBJECT  OF  THE  PRESENT  INVESTIGATION. 

Such  was  the  situation  at  the  beginning  of  the  present  in- 
vestigation. The  object  in  view  has  been  to  try  out  various  phases 
of  sulfur  analysis  by  several  different  methods;  to  see  what 
methods  seem  to  show  the  greatest  possibilities  for  usefulness; 
and  how  they  might  be  modified  or  improved.  All  in  the  hope  that 
a method  might  be  determined  upon  which  would  be  reliable,  simple 
to  carry  out,  and  applicable  to  a greater  variety  of  oils  than 
the  metnous  now  usee.  ^ cannot  s e c 1 e i m c, u u n a t s u c n a nc^.e  <■  uo 
realized  in  the  present  work.,  But  useful  information  was  gained 
concerning  the  application  of  tsc  metaods  tried. 

VI  EXPERIMENTAL. 

The  work  done  can  be  grouped  roughly  under  four  heads: 

(A)  Application  of  the  peroxide  bomb;  (B)  Work  on  op^n  fusion 
methods;  (C)  Work  on  the  Ro the  and  Tiiittum  methods;  and 
(D)  Determination  of  304_~  in  solution. 

(A) 

The  Parr  peroxide  bomb89  is  a simple  and  easily  manipulated 
piece  of  apparatus,  and  its  use  in  the  complete  oxidation  of  oil 
samples  for  sulfur  determinations  is  becoming  more  and  more  pop- 
ular. Some  laboratories  use  this  method  almost  exclusively,  A 


. 


. 

(IS) 

case  in  point  is  the  work  of  Franks8'-,  in  which  he  analyses  shale 
oils  and  a complete  sex  1 s o oi  shale  oil  ^.xacuions  o j t h i s m e t n o d . 
Ihe  method,  as  applied  by  Franks,  is  as  follows; 


One  me us ure  of  sodium  peroxide  [uuout  14  g.j,  1 g. 
of  powdered  po t as s i um . chlor a te  and  0.0  g.  ox  sen- 
zoic  acid  are  placed  in  a Psrr  borne  and  well  mixed 
by  shaking.  About  0.5  g.  of  the  uniform  s aisle  is 
weighed  into  this  mixture  by  means  of  a medicine 
dropper  and  a smell  weighing  bottle.  Ihe  who  © 
mass  is  then  thoroughly  mixed  over  a piece  oi  gla- 
red paper  with  a thin  glass  rod,  any  solids  ad- 
hering to  the  rod  or  falling  on  the  paper  oeing 
subsequently  returned  to  the  bomb.  After  ignition 
in  the  usual  manner  the  fusion  is  carefully  dis- 
solved in  about  50  cc.  of  water,  the  bomb  ohox-ou— 
ghly  washed  with  water,  the  inside  being  finally 
rinsed  with  about  1 cc.  of  concentrated  i* 01  and 
a little  more  water,  and  the  solution  made  acid 
with  concentrated  HC1.  About  5 cc.  of  s at y rated 
bromine  water  is  then  added  to  oxidise  ail  the 
sulphur  to  sulphuric  acid  and  the  iron  to  the  # 
ferric  condition  f i f not  already  in  that  condi- 
tion] and  the  solution  boiled  to  decompose  the 
KaQa  and  expel  the  Bra.  Ammonia  is  added  until 
the  liquid  is  alkaline  and  the  solution  brought 
to  a.vigorous  boil  to  coagulate  the  ferric  hy- 
droxide and  expel  the  excess  of  ammonia  [sso 
2,  under  kISCELL ANEOUS  PGIhTSj.  The  former  is 
then  filtered  off,  a small  waa  of  absorbent 
cotton  being  placed  in  the  bottom  of  the  fil- 
ter to  hasten  the  operation  and  facilitate 
washing.  Jour  thorough  w a s h i n g s with  hot  water 
are  sufficient.  The  solution  is  acidified  with 
1 cc.  of  concentrated  PCI  t using  methyl  orange 
indicator,  adding  1 cc.  in  excess102],  made  up 
to  22a  cc.,  brought  to  a boil  and  5 cc.  of  10 
per  cent  barium  chloride  solution  is  added  slowly 
from  a pipette.  The  boiling  is  continued  until 
the  precipitate  is  'well  fox'med,  which  sometimes 
requires  as  much  as  twenty  minutes.  Ab  out  200 
co.  of  liquid  will  remain.  After  standing  over 
night  the  precipitate  is  filtered  througn  a 
close  7 cm.  filter  paper  (Munkt el 1 s ho.  00  is 
preferred;  and  is  carefully  washed  free  from 
chlorides . 


In  general  the  method  quoted  is  a good  one,  and  could  be 


questioned  in  few  particulars.  Ihe  writer  tried  varying  proportions 
of  KCIO3  and  CqH5C00H,  and  found  those  given  are  about  the  best. 

Very  few  incomplete  fusions  were  encountered  wuen  tne  accelerator 
was  weighed  out  with  fair  accuracy,  but  failures  were  frequent  if 
the  right  amounts  were  not  used.  It  might  be  questioned  if  four 
washings  of  the  voluminous  Fe(0H)s  precipitate  are  enough  to  entire- 
ly free  it  from  SC4_~.  Efforts  were  made  to  demonstrate  that  slight- 
ly higher  results  would  be  obtained  by  dissolving  tae  precipitate, 
diluting  the  solution  and  then  precipitating  the  Fe(CH)2  again. 


. 


. 

' 


( 19) 

It  was  found  in  practice,  however,  that  the  added  step  in  the 
procedure  did  little  more  than  make  it  difficult  to  obtain  good 
checks.  In  addition  it  increased  the  concentration  of  ammonium 
salts  in  solution,  which  is  undesirable102.  The  amount  of  Barium 
chloride  used  can  be  criticised  in  this  as  well  as  most  standard 
methods,  but  this  point  will  be  touched  upon  more  fully  under  (D) . 

Using  this  method  Franks  obtains  checks  which  are  within  one 
percent  of  error  from  their  mean  with  oils  containing  .5 % or  more 
of  sulfur y and  successfully  analyses  fractions  containing  as  low 
as  .3%  of  sulfur.  The  latter  figure  is  perhaps  about  the  minimum 
for  satisfactory  results  with  this  method.  This  for  the  reason 
tnat  wi tn  sucu  small  quantities  o - s a d s L a nc e , a small  loss  of 
material  or  error  in  weighing  would  cause  a relatively  large  error- 
in  the  result.  For  example,  with  a .5  g.  sample  of  oil  containing 
.3a  S,  or  . CO  1 5 g.  S,  corresponding  to  about  II  mg.  of  BaSCU,  an 
error  of  .2  mg.  in  one  weighing  would  cause  a 2%  error  if'  all  the 
other  operations  in  the  analysis  were  perfect. 

The  peroxide  bomb  method  was  first  tried  on  a sample  of 
Louisiana  crude  oil,  using  the  procedure  given  by  Franks.  Ten 
individual  samples  were  analyzed  to  see  how  tiie  checks  were  runn- 
ing. It  was  found  that  slight  errors  in  weighing  came  out  a s large 
errors  in  the  final  results,  but  with  careful  work  good  results 
could  be  obtained  and  repeated.  The  last  pair  of  samples  came  out 
•122%  S and  ,732%  S respectively.  Thereafter  the  standard  of  agree- 
ment between  checks  was  taken  as  .02%  of  total  sulfur.  It  might  be 
added,  however,  that  such  would  be  altogether  unsatisfactory  for 
oils  of  very  low  sulfur  content. 


• 

. 

(20) 

The  next  oil  tried  by  this  me  thou  was  a gasoline  engine 
cylinder  oil.  The  runs  on  this  oil  were  of  value  only  in  demon- 
strating that  this  method  could  not  be  applied  on  such  a low 
sulfur  oil.  Results  obtained  ranged  between  .03$  S and  . 17$  S. 

A comparison  between  this  method  and  the  oxygen  bomb  method 
was  made  using  a sample  of  California  crude  oil,. which  was  the 
oil  used  in  all  later  experiments  on  methods..  Two  samples  ana- 
lyzed 1.005$  and  .990$,  giving  a mean  of  .998$  S,  as  compared  with 
1.003$  S,  the  average  of  4 determinations  with  the  oxygen  bomb. 

In  general  the  peroxide  bomb  method  was  found  to  check  well 
with  the  oxygen  bomb,  without  correction  for  sulfur  in  the  reagents. 
Care  was  always  exercised  that  the  reagents  were  the  best  obtain- 
able (the  Na202  prepared  especially  for  the  purpose),  and  that  they 
were  not  contaminated  witn  laboratory  vapors. 

(E) 

The  simple  technique  of  a dry  fusion  method  is  rather  entic- 
ing to  the  analyst.  If  one  could  mix  the  sample  with  a small  quan- 
tity of  powdered  reagent,  burn  it  off,  dissolve  it  and  determine 
the  sulfate  from  the  solution,  the  question  of  routine  sulfur  an- 
alysis would  be  solved.  A large  number  of  samples  could  be  weighed 
out  and  burned  off  simultaneously,  nothing  in  the  way  of  special 
apparatus  would  be  required,  and  the  operations  would  be  easy. 

An  attempt  was  made  to  utilize  the  oxidizing  principle  of  the 
peroxide  bomb,  by  using  Ka2C2  mixed  with  various  other  substances 
to  be  ignited  in  an  open  dish.  The  advantage  sought  was  that  of 
using  larger  samples  of  oil  than  can  be  used  in  the  peroxide  bomb. 


r • ; -v 


(21) 


Mixtures  of  Na202,  MgO,  and  Na2C03  (using  5 g.  samples  of  Califor- 
nia crude)  were  tried.  The  reagents  were  thoroughly  mixed  with  the 
oil  sample  in  a porcelain  dish,  then  the  mass  was  ignited  by  heat- 
ing the  dish  cautiously.  The  object  was  to  dilute  the  Na202  to 
such  an  extent  that  the  fusion  would  travel  quietly  throughout  the 
mass.  It  was  found,  however,  that  the  oxidation  was  in  ail  cases 
so  vigorous,  even  when  the  oil  and  Ma202  were  greatly  diluted, 
that  particles  of  the  reacting  mass  were  always  carried  off  in 
the  flame.  This  held  true  even  when  the  Na2C2  was  entirely  omit- 
ted from  the  mixture,  except  when  only  Na2C03  was  mixed  with  the 
oil.  In  the  latter  case  the  residue  consisted  of  a caked  material 
with  carbonaceous  matter  imbedded  in  the  mass.  The  latter  could 
not  be  successfully  burned  to  an  ash,  for  it  assumed  a pasty  con- 
sistency when  heated. 

Calcium  peroxide  was  the  next  oxidising  agent  tried.  It  was 
first  mixed  with  Na2C03,  but  the  activity  seemed  to  be  slignt. 

Then  the  Ca02  was  mixed  with  the  oil  alone  and  heated.  Oxidizing 
action  was  evident,  the  mixture  giving  off  dense  fumes  during  the 
action.  The  most  encouraging  feature  with  the  Ca02  was  that  the 
mixture  after  ignition  was  light  and  powdery,  containing  very 
little  carbon,  and  that  easily  burned  off.  The  method  was  tried 
quantitatively  by  mixing  10  g.  Ca02  with  about  3 g.  of  oil.  This 


a Sample  from  Bausch  and  Lomb  Optical  Co.,  known  to  have  been 

in  stock  over  IS  years.  Not  more  than  a trace  of  sulfur  in  it. 
Another  sample,  commercial  grade,  was  tried  but  it  was  loaded 
with  sulfate.  For  the  last  trials  a new  s amp le  of  CaOs  was 
obtained,  which  was  fresh  and  much  more  reactive  than  the 
previous  samples.  It  contained  a small  amount  of  sulfate, 
but  blanks  were  run  in  every  case. 


(22) 

mixture  was  ignited  by  carefully  heating  one  edge  of  the  dish, 
when  the  fusion  would  start  spontaneously  and  creep  throughout 
the  mass,  white  fumes  being  given  off  meanwhile.  After  the  reac- 
tion was  completed  the  organic  matter  was  completely  burned  off, 
the  ash  dissolved  in  HC1  and  filtered,  and  the  S04 — in  the  fil- 
trate precipitated  with  BaCl2.  Average  of  the  two  samples  was 
.383%  S on  the  California  crude  containing  1.0%  S.  When  a large 
amount  of  the  Ca02  was  taken  (20  g.  with  1.5  g.  oil),  the  result 
was  .579%  S,  after  correcting  for  blanks  on  the  reagents,  which 
correction  was  made  in  every  case  in  this  phase  of  the  work. 

The  next  oxidisinfe  agent  tried  was  Ba02.  It  was  hoped  that 
the  method  proposed  by  Schillbach62  could  be  used.  It  is  the  most 
direct  method  that  has  ever  been  proposed.  It  consists  in  mixing 
the  sample  with  BaC2,  heating  the  mixture  to  start  the  reaction, 
burn  off  any  residual  carbon,  dissolve  the  ash  in  HC1  and  weigh 
the  insoluble  matter  as  EaS04»  Various  proportions  of  Ba02  and 
oil  were  tried,  but  the  reaction  always  ended  in  a melt  which  was 
hard  to  free  from  residual  carbon  and  formed  a hard,  horny  mass 
when  cooled.  It  was  found  that  this  horny  residue  would  become 
more  friable  upon  standing  in  moist  air,  but  the  method  was  aban- 
doned because  of  the  difficulty  of  igniting  the  residue  to  a sat- 
isfactory ash. 

A desirable  ash  could  be  obtained,  it  was  found,  by  using  a 
mixture  of  BaC2  and  CaC2,  and  some  runs  were  made  with  this  mix- 
ture. After  correcting  for  a large  tare  in  the  blanks,  the  result- 
ant sulfur  was  only  .412%.  This  was  in  using  CaC2  of  doubtful 
strength,  however,  so  a new  sample  was  obtained.  The  reaction 


(23) 


with  the  new  Ca02  in  the  mixture  was  much  more  vigorous  than  with 
the  old,  but  the  net  result  was  about  the  same.  In  fact  it  was 
found  that  all  the  runs  made  with  the  Ba02  or  mixtures  thereof 
had  such  a high  sulfur  content  in  the  blanks  as  to  make  the  results 
erratic.  When  so  much  sulfur  was  present  in  the  reagents,  and  the 
latter  were  weighed  out  on  rough  balances,  little  could  be  hoped 
for  in  the  way  of  accuracy.  Qualitative  tests  on  the  reagents 
individually  showed  not  more  than  a trace  of  sulfur  in  the  new 
sample  of  Ca02,  but  the  BaC2  which  had  been  used  all  along,  and 
which  was  supposedly  pure,  was  found  to  be  loaded  with  sulfate. 

Attempts  to  use  the  fresh  CaC2  alone  were  unsuccessful  be- 
cause the  reaction  was  so  vigorous  that  considerable  of  the  react- 
ing mixture  was  thrown  out  of  the  dish.  It  was  tried  in  a beaker 
covered  with  a watch  glass  and  also  a lightly  covered  flask,  with 
the  same  condition  obtaining.  A mixture  of  Ca02  and  Ba02  had  been 
tried  in  a small  steel  bomb  and  the  bomb  exploded,  so  the  CaC2 
alone  was  not  tried  in  a bomb.  Sodium  carbonate  was  tried  as  a 
diluent  with  the  Ca02,  but  the  percent  sulfur  given  by  this  method 
was  .650$,  or  roughly  two-thirds  of  the  actual  sulfur  content.  The 
proportions  used  were,  10  g.  Ca02,  S g.  Ua2C0s,  and  1.5  g..  of  oil. 
Using  half  the  amount  of  reagents  in  the  same  proportion,  with 
about  the  same  amount  of  oil,  resulted  even  lower,  .54!$  S. 

In  concluding  the  trials  with  the  open  fusion  method,  it  may 
be  said  that  the  results  are  disappointing.  Although  an  accurate 
open  fusion  method  may  be  developed,  possibly,  none  of  the  methods 
tried  to  date  are  accurate.  If  it  is  a choice  between  the  Eschka 
method,  and  the  Ca02-Na2C03  method  last  tried,  the  writer  would 


(24) 

choose  the  latter.  It  is  easy  to  manipulate,  but  even  with  the 
oxidizing  agent  present  the  results  are  low. 

Open  dry  fusion  methods  proposed  are  all  subject  to  loss  of 
sulfur.  There  is  no  doubt  that  a considerable  amount  of  the  sulfur 
content  of  the  oil  is  lost  through  volatilization  of  light  frac- 
tions in  the  initial  stages  of  the  reaction,  and  although  the 
presence  of  oxidizing  agents  may  help  to  conserve  the  sulfur  at 
this  point,  the  loss  is  still  appreciable.  Where  the  reaction  is 
at  all  vigorous  there  is  also  the  tendency  of  mechanical  loss.  On 
the  other  hand,-  if  the  reaction  is  not  vigorous  enough,  and  much 
carbonaceous  matter  is  left  in  the  end,  the  sulfur  already  caught 
in  the  alkali  may  be  lost  again  through  reduction  to  decomposable 
sulfites  by  the  incandescent  carbon  or  CC  present  in  the  burning 

y 

off.  Loss  in  thisAwas  later  prc  with  experiments 

on  the  Ho  the  and  7/hit  turn  methods. 

(C) 

Whittum92  developed  a combination  method  at  the  Universi  ty 

of  Illinois,  and  some  further  data  concerning  it  was  obtained  by 

Otsubo98.  The  method  was  first  proposed  as  a substitute  for  the 

lamp  method  and  intended  for  light  burning  oils.  An  effort  was 

made  to  prove  its  reliability,  and  also  to  extend  its  use  to  a 

wider  variety  of  fractions.  The  procedure  is  as  follows: 

Y.'eigh  £—  1C  g . cf  the  oil  into  a porcelain  disa. 

Cuts  I . h— . t g.  of  finely  powdered  KBr  over  the 
surface.  Add  4— E cc.  of  fuming  nitric  acid, 
drop  by  drop,  with  constant  stirring.  After 
the  reaction  has  ceased,  place  the  dish  on  a 
steam  bath  or  asbestos  pad  and  evaporate  the 
liquid  until  it  becomes  viscous.  Acid  about  h 
A . of  Eschka  mixture  and  mix  thoroughly  with 
the  oil,,  being  careful  to  take  up  all  ohe  oil 
that  may  adhere  to  the  sides  of  the  dish. 

Place  trie  dish  over  an  alcohol  flame,  or 


(25) 

Eur.een  protected  with  an  asbestos  pad,  and 
allow  the  mixture  to  dry  slowly.  The  heat 
should  be  increased  gradually  until  the 
mixture  catches  fire  and  burns  tc  a white 
powder,  breaking  up  the  large  particles 
occasionally  with  a glass  rod.  After  cool- 
ing add  water  and  ECl  to  dissolve  the  resi- 
due and  filter  the  solution.  The  SC4 — in 
the  filtrate  is  precipitated  in  the  usual 
manner. 

Leaving  aside  the  question  of  whether  the  method  retains  all 
the  sulfur  in  lamp, oil,  its  behavior  with  crude  oil  was  studied. 
Certain  difficulties  were  encountered  using  this  method  with  crude 
oil,  and  considerable  work  was  done  to  try  to  eliminate  them;  and, 
when  the  procedure  could  be  modified  to  suit  a heavier  oil,  to  see 
what  results  could  be  obtained  by  it. 

The  first  difficulty  encountered  was  in  the  addition  of  the 
fuming  nitric  acid.  Even  adding  it  very  slowly,  drop  by  drop,  the 
reaction  was  always  so  violent  that  some  of  the  oil  would  spatter- 
out.  Benzene  ’was  tried  as  a diluent  to  cut  down  the  violence  of 
the  reaction  somewhat.  The  spattering  was  diminished  by  the  benzene, 
but  not  entirely  eliminated.  The  results  of  duplicate  samples  us- 
ing the  benzene  were  a trifle  higher  that  those  obtained  by  the 
straight  Whittum  method,  so  it  was  seen  that  the  diluent  in  no 
way  effected  loss  of  sulfur.  It  was  then  resolved  to  try  inert 
solvents.  Chloroform,  tetraclilor  ethane,  and  carbon  tetrachloride 
were  tried,  and  of  these  the  latter  seemed  the  best.  Quantitative 
runs  using  different  amounts  of  CCi4  failed  to  show  any  diminution 
in  the  amount  of  sulfur  obtained,  and  tiie  results  were  in  some 
cases  higher.  It  was  concluded  that  the  addition  of  enough  CC14 
to  cut  down  the  violence  of  the  reaction  had  no  undesirable  effect, 
and  was  to  be  recommended.  The  method  is  to  mix  the  CC14,  say 
about  15-20  cc.,  with  the  oil  and  then  to  add  the  fuming  nitric 


. 


(26) 


acid  slowly. 

The  next  difficulty  met  in  the  Whittum  method  was  that,  if 
the  sample  were  heated  for  a time  to  concentrate  the  residue 
after  the  addition  of  the  fuming  nitric  acid  and  before  adding 
the  Eschka  mixture,  the  mass  would  solidify  when  it  was  attempted 
to  stir  in  the  latter,  and  a uniform  mixture  was  impossible  to 
obtain.  It  was  found  that  a good  mixture  could  be  obtained  if  the 
Eschka  reagent  were  mixed  with  the  oil  directly,  or  very  shortly 
after  the  reaction  with  the  fuming  nitric  acid  had  subsided. 

Another  mechanical  difficulty  tnat  was  encountered  was  the 
fact  that  when  igniting  the  Eschka  mixture  at  the  end  to  complete- 
ly burn  out  the  residual  carbon,  the  mass  would  assume  a pasty 
consistency  and  be  hard  to  nandle.  This  could  be  obviated  by  in- 
creasing the  proportion  of  MgO  in  the  mixture. 

As  the  chief  mechanical  difficulties  seemed  to  have  been  met, 
quantitative  runs  were  made  on  the  California  crude  oil,  of  1.0$ 
sulfur  content.  The  Whittum  method  modified  only  by  adding  the 
Eschka  mixture  directly  after  the  reaction  with  fuming  nitric  acid 
had  ceased  gave  .684$  S.  The  same,  except  that  an  inert  solvent 
was  added  before  the  fuming  nitric  acid,  gave  .727$  S.  Varying  the 
amounts  of  fuming  nitric  acid  and  of  MgO  and  Na2C02,  results  were 
obtained:  .758$,  .768$,  .734$,  .813$,  and  .749$.  It  was  found  that 
a larger  percent  of  sulfur  could  be  obtained  by  increasing  the 
amount  of  fuming  nitric  acid  to  about  7 cc.  A larger  percent  of 
Fa2C02  in  the  absorbing  mixture  had  the  same  effect,  but  the  limit 
for  the  method  was  the  highest  figure  given,  .813$  S,  and  this 
was  obtained  without  correcting  for  sulfur  in  the  reagents.  Also 


(27) 

the  larger  amount  of  Na2C03  used  made  the  residue  difficult  to 
handle,  and  it  was  ignited  for  several  hours  in  the  effort  to 
obtain  a white  ash.  It  is  probable  that  in  this  time  some  sulfur 
was  absorbed  from  the  laboratory  fumes. 

It  was  thought  that  perhaps  an  absorbent  present  at  the  time 
the  fuming  nitric  acid  were  added  would  conserve  the  sulfur.  An- 
hydrous MgCl2  was  first  tried,  for  the  reason  that  it  would  in  no 
wise  take  up  the  energy  of  the  oxidizing  acid  as  would  MgO  or 
Na2C0E,  and  could  at  the  same  time  unite  with  the  less  volatile 
S04““,  HC1  escaping.  But  only  .328%  of  sulfur  was  obtained  in 
this  attempt. 

Another  modification  was  tried,  by  using  anhydrous  SeOCl 2 as 
the  oxidizing  agent.  Some  very  interesting  reactions  ensued,  chief 
among  which  was  the  escape  of  reddish  fumes  of  selenium.  Some  of 
the  sulfur  was  oxidized  to  S04~~,  and  the  residual  Se  was  easily 
gotten  rid  of  in  the  end  by  volatilization  during  the  subsequent 
ignition  of  the  residue.  But  the  oxidation  was  either  incomplete 
or  selective,  for  the  percents  of  sulfur  obtained  by  the  SeOCl2 
were  .278%  and  ,290%  in  two  runs. 

The  last  trial  of  the  Whit  turn  method  was  made  about,  as  the 
first,  using  the  larger  amount  of  fuming  nitric  acid  with  smaller 
samples  (2. 5-3.0  g.),  and  then  during  the  ignition  with  the  Eschka 
mixture,  the  dishes  were  piled  full  of  MgO  to  force  the  escaping 
gases  to  travel  through  a thick  layer  of  absorbent  before  they 
could  escape.  The  fact  that  I. 108%  of  sulfur  was  obtained  in  this 
run  was  not  taken  as  proving  that  all  the  sulfur  could  be  obtained 
by  this  method,  but  rather  as  an  indication  that  other  sources  of 


* 


(28) 


error  were  being  multiplied,  e.g.,  high  concentration  of  Mg  salts 
causing  occlusion  in  the  EaS04  precipitate;  and  sulfur  in  the  re- 
agents, for  which  no  correction  was  made.  In  later  experiments  it 
was  proven  that  in  this  general  type  of  procedure  the  sulfur  is 
lost  in  two  ways:  by  volatilization  during  the  addition  of  the 
fuming  nitric  acid,  and  by  reduction  to  S02  and  consequent  volatil- 
ization or  otherwise  in  the  burning  off  of  the  residue.  In  view 
of  these  facts  it  will  be  seen  that  even  if  all  the  sulfur  could 
be  retained  in  the  burning  of  the  residue,  by  passing  the  escaping 
gases  through  a large  quantity  of  absorbing  alkali,  there  would 
still  have  been  the  loss  encountered  at  the  initial  stage  in  the 
analysis.  The  Whit turn  (and  Rothe)  type  of  sulfur  analysis  was  held 
to  be  inherently  at  fault  in  these  respects,  at  least  as  applied 
to  crude  oils.  Reasoning  by  analogy  it  might  be  questioned  whether 
such  methods  are  reliable  on  low  sulfur  oils.  Of  course  the  total 
error  in  sulfur  with  a low  sulfur  oil  would  be  small,  in  propor- 
tion with  the  small  amount  of  total  sulfur,  but  the  results  by 
the  Whittum  type  of  procedure  might  still  be  questioned. 

The  method  of  Waters  is  essentially  the  same  as  the  Whittum 
method,  except  that  Waters  uses  fuming  nitric  acid  which  is  sat- 
urated with  bromine.  This  method  was  not  tried  in  the  present  in- 
vestigation. 

The  Rotiie  method  has  come  into  some  favor,  as  shown  by  the 
fact  that  it  has  been  tentatively  adopted  by  the  A.S.T.M.;  and 
the  recent  work  of  Vandaveer96  would  seem  to  recommend  it.  The 
principles  of  the  method  are  the  same  as  in  the  Whittum  method, 
variations  in  procedure  being  that  the  operation  is  carried  out 


(29) 


in  a flask,  that  the  absorbing  material  (MgO)  is  added  before  the 


addition  of  fuming  nitric  acid,  and  that  a large  excess  of  the 


latter  is  used.  The  procedure  recommended  by  Vandaveer: 


Weigh  from  5 to  10  grams  of  oil  into  a liter 
pvrex  flask  containing  2 grams  of  magnesium  qxi de . 
Immediately  add  carefully  25  cc.  of  fuming  nitric 
acid.  Allow  the  mixture  to  stand  until  the  reac- 
tion-ceases, Then  heat  gently  on  a sand  bath  for 
about  three-quarters  of  an  hour.  At  the  end  of 
that  time  gradually  raise  the  temperature  until 
all  the  nitrates  are  decomposed.  Continue  the 
heating  over  a full  Bunsen  flame  for  several 
minutes.  Blow  in  air  or  oxygen  and  heat  the 
flask  with  a free  flame  to  drive  off  the  carbon. 
Cool  the  flask,  moisten  the  white  residue  with 
water,  add  concentrated  hydrochloric  . a<?id  and 
heat.  Filter  of r the  carbon  and  precipitate  the 
sulfur  as  barium  sulfate  in  the  usual  manner. 


Six  analyses  were  made  of  the  California  crude  oil  by  the 


Rothe  method.  The  first  two  (without  modification,  except  that 


500  cc.  flasks  were  found  to  be  more  convenient,  on  the  whole. 


than  liter  flasks)  gave  . 685%  5.  The  next  three,  modified  by  add- 


ing 20  cc. of  CCI4  before  treatment  with  the  fuming  nitric  acid, 
gave  .782$,  .786$,  and  .751$,  respectively.  The  last  was  low  again, 
.686$  S.  Taking  the  average  of  the  three  in  closest  agreement,  the 
result  by  the  Rothe  method  is  .773$  of  sulfur,  as  compared  with 
.734$  of  sulfur,  the  average  of  the  ten  best  by  the  Whittum  method, 


or  modifications. 


It  can  be  concluded  from  the  above  that  the  Rothe  method 


gives  slightly  better  results  than  the  Whittum  method,  but  loss 
of  sulfur  occurs  in  both  cases.  Also,  the  fact  is  further  demon- 


strated that  addition  of  an  inert  diluent  for  cutting  down  the 


violence  of  the  reaction  with  fuming  nitric  acid,  does  not  incur 


additional  loss  of  sulfur.  And  in  case  of  the  Rothe  method  it  was 


found  that,  using  the  crude  oil,  such  an  inert  diluent  is  necess- 


ary to  prevent  the  mixture  taking  fire  when  the  fuming  nitric 


■ 


' 


(30) 

acid  is  added.  The  CC14  used  served  as  an  excellent  preventative 
in  this  respect. 

The  Rothe  method  was  also  tried  on  a sample  of  heavy  Mexican 
crude  oil,  which  analyzed  4.940^  of  sulfur  by  the  peroxide  bomb 
method.  The  Rothe  method  gave  ! . 6 70%  of  sulfur.  App  arently  the 
higher  the  sulfur  content  of  the  oil,  the  greater  is  the  loss  in 
sulfur  by  the  Rothe  or  similar  methods.  It  might  well  be  argued 
that  the  converse  is  true:  that  the  lower  the  percent  of  sulfur 
in  the  oil,  the  more  accurate  is  the  method;  and  that  inasmuch  as 
the  Rothe  method  has  been  used  largely  for  low  sulfur  oils,  it  is 
in  no  wise  to  be  condemned  because  it  gives  unsatisfactory  results 
with  high  sulfur  oils.  Such  may  be  the  case,  but  the  writer  is  of 
the  opinion  that  the  same  principles  which  govern  the  loss  of  sul- 
fur with  a high  sulfur  oil  'would  also  pertain  to  a low  sulfur  oil. 
If  so,  the  Rothe  method  could  only  be  applied  on  oils  so  low  in 
sulfur  that  the  loss  of  sulfur  by  the  method  comes  within  the  ex- 
perimental error.  It  would  be  necessary  to  make  a whole  series  of 
comparative  runs  on  a series  of  oils  of  gradually  differing  sul- 
fur content  to  find  out  exactly  where  this  point  is.  Even  then 
there  would  be  the  uncertainty  as  to  whether  the  method  would  be 
equally  accurate  with  two  oils  of  the  same  total  sulfur  content, 
but  of  different  properties.  The  difficulty  with  the  method  is  to 
know  where  to  draw  the  dividing  line-  which  analyses  to  trust,  and 
which  to  view  with  suspicion. 

It  might  also  be  argued  that  the  type  of  sulfur  compounds  in 
low  sulfur  oils  are  easily  handled  by  the  Rothe  method,  but  that 
the  method  is  not  designed  to  oxidize  the  free  sulfur  or  some  of 


(31) 

the  more  refractory  sulfur  compounds  of  crude  oils.  The  argument 
is  hardly  tenable,  ’however,  since  fuming  nitric  will  readily  and 
completely  oxidize  free  sulfur  to  sulfuric  acid.  It  seems  that 
loss  is  incurred  by  such  factors  as  premature  volatilization  and 
loss  in  the  burning  off  rather  than  by  insufficient  oxidizing 
strength  to  attack  all  the  forms  of  sulfur. 

To  obtain  some  idea  as  to  just  where  the  loss  of  sulfur  is 
incurred  in  these  methods,  approximately  30  g.  of  the  California 
crude  oil  were  taken  in  a large  porcelain  dish,  with  50  cc,  of 
CC14,  and  about  2 g,  of  KBr.  Thirty  cc.  of  fuming  nitric  acid  were 
added  with  stirring,  and  after  the  reaction  had  subsided  the  dish 
was  warmed  gently  for  a time  to  concentrate  the  mixture.  Before 
it  became  too  viscous,  about  10  g.  of  Eschka  reagent  was  added  and 
the  whole  thoroughly  mixed  with  a steel  spatula.  The  residue  was 
then  moulded  into  a circular  cake  and  quartered,  two  opposite 
quarters  being  taken  for  ignition  in  the  regular  Wkittum  style, 
and  three  representative  samples  being  taken  from  the  remaining 
quarters  for  ignition  in  a peroxide  bomb.  The  latter  analyzed 
.700$,  .716$,  and  .709$  sulfur  respectively,  or  an  average  of 
.708$  S-  The  samples  burned  off  in  the  usual  Whittum  style  ana- 
lyzed .576$  and  .597$  S,  or  an  average  of  .587$  sulfur. 

It  is  seen  from  this  experiment  that  JO Q j . 70  8- . , 587)  = !7.  !$ 

of  the  sulfur  is  lost  in  the  burning  off  of  the  oily  alkali  resi- 
due in  the  Whittum  method.  The  total  loss  of  sulfur  by  tiie  Whittum 
method  (taking  the  average  of  ten  runs,  of  .734$)  is  seen  to  be 

= 26.6$  of  the  sulfur  originally  in  the  oil.  Of  this 

1.0 

total  loss,  the  remaining  9.5$  (26. 6$-  ! 7.  1$)  of  the  original  sul- 


. 


(32) 

fur  evidently  is  lost  by  volatilization  in  the  initial  stage  of 
the  process. 

In  concluding  the  discussion  of  this  phase  of  the  work  it 
seems  evident  that  approximately  one  fourth  of  the  total  sulfur 
of  the  crude  oil  in  question  is  lost  in  the  methods  which  depend 
upon  initial  oxidation  with  fuming  nitric  acid,  together  with  ig- 
nition of  the  residue  with  alkalis.  Of  the  sulfur  lost,  roughly 
one  third  is  lost  by  volatilization  in  the  initial  stage  when  the 
fuming  nitric  acid  is  added,  and  the  remainder  is  lost  by  reduction 
to  S02  and  consequent  escape,  or  otherwise  in  the  ignition  of  the 
residue.  It  is  not  claimed  that  these  proportions  would  hold  for 
other  types  of  oils,  but  at  least  it  seems  certain  that  sulfur  is 
lost  at  both  points,  and  that  such  a loss  would  be  incurred  in  a 
greater  or  less  degree  with  any  oil. 

(C) 

The  problem  of  sulfur  analysis  has  not  been  entirely  solved 
by  any  means  when  the  sulfur  is  obtained  as  S04~~  in  solution  103 
104  ,0B,  notwithstanding  the  fact  that  most  methods  usually  con- 

clude the  details  of  the  procedure  by  some  such  statement  as,  n And 

the  sulfur  in  the  filtrate  precipitated  with  PaCl2  in  the  usual 

r / 

manner. 

As  intimated,  the  standard  procedure  is  to  precipitate  the 
S04“~  from  the  slightly  acidified  solution  by  means  of  BaCl2, 
weigh  the  precipitate  as  BaS04  and  calculate  to  percent  of  sulfur 
in  the  sample. 

For  the  best  work,  after  boiling  the  mixture  it  should  be 


-Tool 

allowed  to  stand  over  night  to  allow  the  EaS04  precipitate  to 
form  into  as  large  crystals  as  possible,  and  this  is  a slow  pro- 
cedure. Even  without  standing  over  night,  the  usual  gravimetric 
procedure  is  somewhat  slow  and  tedious. 

For  more  rapid  work  there  are  several  modifications  which 
can  be  used  with  very  little  sacrifice  in  accuracy.  Chief  among 
these  are  the  Parr  photometric  method106,  and  the  method  whereby 
the  sulfur  is  precipitated  as  benzidine  sulfate  with  subsequent 
titration  of  the  latter  by  KMn04  in  acid  solution107  ,08.  Another 
method,  of  the  volumetric  type109,  is  to  add  an  excess  of  PaCrC4 
to  the  solution.  The  reaction  will  go  slowly  to  completion  to- 
wards the  formation  of  BaS04.  The  amount  of  PaS04  formed  can  be 
determined  indirectly  by  titrating  the  equivalent  amount  of  CrC4~" 
left  in  solution  by  means  of  standard  iodine.  Still  another  method, 
this  of  a semi-volumetric  nature,  is  that  proposed  by  Bucherer'10. 
Here  the  solution  is  diluted  to  500  ec.,  and  standard  EaCl2  solu- 
tion is  added  to  aliquot  portions,  the  exact  amount  to  be  added 
being  determined  by  filtering  off  a few  cubic  centimeters  each 
time  and  testing  the  small  filtered  portions  with  a drop  of  H2S04 
or  a drop  of  BaCl2  to  see  which  is  in  excess. 

None  of  these  methods  were  tried  in  the  present  investigation. 
Their  usefulness  lies  chiefly  where  routine  sulfur  determinations 
are  to  be  made  daily,  where  with  a careful  standardization  of  pro- 
cedure very  good  accuracy  can  be  obtained. 

The  Parr  photometric  method  is  doubtless  the  most  rapid  of 
those  given.  It  requires  a special  form  of  photometer,  but  in 
laboratories  making  routine  sulfur  analyses  the  latter  would  be 


v j : . l J • ' ■■  ■ ■ • j j 

; • ■ « ■ > \ 


( r . 


I 


. ; ■ ;■  ■:  i » 


(34) 

a justifiable  outlay.  The  method  is  to  make  up  the  solution  to 
be  tested  to  250  cos.,  taking  50  cc.  of  this  solution,  diluting 

to  !00  cc.  and  adding  an  excess  of  sized  BaCl2  crystals.  This 
results  in  a finely  divided,  non-settling  precipitate.  The  tur- 
bidity of  the  solution  is  a direct  factor  of  the  amount  of  sul- 
fur, which  can  be  obtained  by  direct  translation  of  the  photometer 
reading  by  means  of  a curve.  The  method  is  surprisingly  accurate, 
when  the  eye  of  the  operator  has  once  been  standardized  by  com- 
parison with  solutions  of  known  sulfur  content.  It  has  another 
advantage,  also,  that  the  relative  error  is  no  greater  with  a low 
percent  of  sulfur  than  with  a high  percent. 

The  method  using  a BaCr04  suspension  as  the  precipitant  is 
interesting;  but  it  is  thought  doubtful  if  the  method  proposed  by 
Bucherer  would  be  found  satisfactory. 

The  recognised  standard  procedure,  however,  is  the  gravimet- 
ric estimation  of  the  BaS04  precipitate.  It  is  also  the  most  prac- 
tical when  only  occasional  analyses  are  to  be  run.  As  there  are 
points  which  are  too  oftei)  lost  sight  of,  some  of  the  variable 
factors  of  this  precipitation  were  tried  out  from  a practical 
standpoint. 

Since  it  is  a well-known  lact103  that  BaCl2  is  apt  to  be  ad- 
sorbed or  occluded  in  a precipitate  of  BaS04  wnen  it  is  forming, 
one  would  expect  to  find  that  standard  methods  for  sulfur  analysis 
would  lay  down  a careful  procedure  to  prevent  such  occlusion.  There 
seems  to  be  a laxity  in  this  respect.  Holde,  the  U.  S..  Bureau  of 

HI. 

Mines,  the  U.  S..  Bureau  of  Standards,  and  Hamor  and  Padgett  (in 
references  cited)  simply  say  that  the  precipitation  of  BaS04  is 


, 


.4 


' 


(35) 

made  with  BaCl2  in  the  usual  manner,  except  that  in  the  Mines 
Bulletin  No.  5,  the  directions  are  to  add  EaCl2  solution  drop  by 
drop  until  there  is  an  excess  present.  Parr  precipitates  by  means 
of  the  addition  of  10  cc.  of  10%  BaCl2«2H20,  regardless  of  whether 
the  oxygen  bomb,  Eschka,  or  peroxide  bomb  methods  are  used.  Franks 
adds  5 cc.  of  10%  BaCl2,  using  the  peroxide  bomb  method.  On  the 
whole,  it  seems  to  be  customary  in  oil  analysis  to  add  10  cc.  of 
10%  barium  chloride  solution. 

Since  too  much  BaCl2  in  solution  may  introduce  an  error  in 
the  results,  the  question  arises  as  to  just  how  much  to  add,  and 
in  what  manner,  so  that  the  error  caused  by  occlusion  of  BaCi2 
in  the  PaS04  will  be  reduced  to  a minimum;  and  at  the  same  time 
have  enough  Ba+  + present  to  completely  precipitate  the  SC4“~. 

From  the  standpoint  of  common  ion  effect,  it  would  seem  desirable 
to  have  a certain  excess  of  Ba  + + in  solution,  to  decrease  the  sol- 
ubility of  the  B aSC4  to  be  recovered . 

Consulting  a table  of  solubility  data,M,  the  solubility  of 
BaS04  in  water  at  room  temperature  is  2.5*!0~3  g.  per  liter.  Say 
precipitation  was  made  in  400  cc.  of  solution,  from  the  fusion  of 
.5  g.  of  oil  (the  amount  taken  by  the  peroxide  bomb  method),  this 
would  mean  that  the  sulfur  which  would  go  undetected,  with  no  ex- 
cess of  Ba*+,  could  be  only  .027%,  due  to  the  solubility  of  BaS04 
in  water. 

Treadwell-Hall ,0 3 recommends  the  addition  of  10  cc.  of  N. 
BaCl2  for  each  gram  of  BaS04  precipitate  to  be  obtained.  With  this 
standard,  let  us  assume  an  analysis  of  a ,5  g.  sample  of  oil  con- 
taining 1%  of  sulfur,  and  see  what  percent  of  sulfur  could  remain 


. A , . 


* 


■ . ' . 


' 


(36) 

undected  in  solution.  The  solubility  product  of  EaS04  is 
!.2l*IO”10,  or  . 000000000  1 2 L In  the  sample  is  .005  g.  of  sulfur, 
which  is  equivalent  to  .03635  g.  of  PaS04.  According  to  our  stan- 
dard, we  shall  therefore  add  .3635  cc,  of  N,  BaCl2. 

Amount  of  BaCl2  added,  in  grams  , 03795 

Theoretical  amount  necessary  . ......  ,03365 

Amt.  BaCl2  in  excess  of  theoretical  ....  .00435 

This  amount  of  EaCl2  in  excess  of  the  amount  necessary  to  precipi- 
tate all  the  sulfur  from  400  cc.  of  solution  is  equivalent  to 
.0000376  gram  ion  concentrat ion  of  Ba+  + , BaCl2  being  72%  ionized. 
The  Pa**  concentration  due  to  the  BaSC4  in  solution  is  .000011, 
giving  a total  Ba+*  concentration  of  .0000436  g.  ion. 

(Ba)  ( S04 ) = .0000  11  x .00001!  = .000000000  12! 

(S04)  = .000000000121  = ^000000000121  = .00000249. 

“(Pa)  .0000486“ 

PaSC4  in  solution  is  the  same  or  .00000249  moles  per  liter.  This 
is  equivalent  to  .00023  g.  of  BaS04  in  400  cc.  of  solution,  and 
on  the  .5  g.  sample  is  equivalent  to  .0063%  of  sulfur. 

In  the  same  manner,  the  amount  of  sulfur  which  could  go  un- 
detected, owing  to  the  solubility  of  PaS04  in  water,  using  the 
amount  of  BaCl2  solution  called  for  by  Treadwell-Hali,  in  a .5  g, 
sample  containing  2%  of  sulfur,  would  be  only  .0036%.  Applying 
the  same  solubility  data  to  an  actual  analysis  of  a sample  of 
Mexican  crude  oil:  sample,'  .5232  g.,  analyzing  4.8  14  % S,  the 
amount  of  sulfur  which  went  undetected  in  this  way  was  only  .0015%. 

Of  course  the  solubility  of  PaSC4  is  somewhat  affected  by 
presence  of  various  salts  in  solution,  as  well  as  free  acid,  but 
such  effects  are  usually  slight  except  for  the  presence  of  acid 


1 


(37) 

( -arid  the  trivalent  metals  such  as  iron,  which  are  removed  hy 
ammonia).  The  acidity  can  be  regulated  by  adding  I cc.  of  HC1 
to  the  neutral  solution  before  addition  of  the  PaCl2. 

It  will  be  seen  that  in  all  these  cases  the  amount  of  sulfur 
which  could  go  undetected  owing  to  the  water  solubility  of  BaS04 
in  the  presence  of  only  a small  excess  of  Fa**  is  well  within  the 
experimental  error,  and  therefore  to  be  disregarded. 

Then  why  add  a larger  excess?  There  is  the  practical  reason, 
of  course,  and  that  is  the  uncertainty  of  the  amount  of  EaSC4  pre- 
cipitate to  be  obtained.  Even  from  this  standpoint  it  would  hardly 
seem  desirable  to  add  so  much  PaCl2  as  10  cc,  of  10$  in  all  cases, 
regardless  of  the  method  or  the  size  of  the  sample.  When  using  the 
peroxide  bomb  method  Franks  has  cut  the  usual  amou'nt  of  PaCl2  in 
half,  and  yet  he  is  adding  enough  for  the  complete  precipitation 
of  13.2$  of  sulfur,  considering  the  necessary  excess  and  the  size 
of  the  sample  taken.  With  the  usual  amount  in  the  peroxide  bomb 
method,  enough  BaCl2  is  added  to  precipitate  26.4$  of  sulfur. 


From  a practical  standpoint,  does  this  unnecessary  excess  of 
BaCl2  usually  obtaining  actually  effect  the  results  appreciably? 
The  following  results  answer  the  question: 


Analyses 

By  I he  Parr 

Peroxide  Bomb. 

$ S obtained 
by  adding  5 
cc.  of  10 % 
BaClg  Eolru 

f,  S obtained 
by  adding  amt, 
£ a C 1 » called 
for  by  Tread- 
wel 1—  Hall 

Increase  in  app  — 
arant  % of  S due 
to  addition  of 
too  much  B aCl  a 

Louisiana  Crude 

0.835  $ 

0. 727  $ 

0.  108  $ 

Mex.  Crude  No..  1 

4.940 

4.8  14 

0.  126 

Mex.  Crude  No.  2 

4.983 

4.819 

0.  164 

In  every  case  the 

filtrate  was 

tested  with  a drop 

of  H2S04  to 

. 

(38) 


make  sure  that  BaCl2  was  in  excess. 

In  view  of  these  considerations,  it  would  seem  advisable  to 
take  into  account  the  size  of  the  sample  and  the  probable  maximum 
percent  of  sulfur  present  when  adding  PaCl2,  and  not  ado.  an  un- 
necessary excess.  In  the  opinion  of  the  writer,  the  me thou  given 

in  one  refers  . 0 of  adding  the  : aOl 2 solution  crop  by  urop  is  no  c 
a practical  one,  for  with  small  amoijuts  of  - ui fur  no  precipitate 

of  EaSC'4  is  visible  at  first,  and  only  after  boiling  does  it  appear. 

Then  it  is  seen  as  a turbidity,  and  it  is  a practical  impossibility 

to  gauge  the  amount  of  tiie  precipitant  which  should  be  add-.  . The 

latter  condition  also  holds  true  for  larger  amounts  01  &uixui . 

The  manner  of  adding  the  BaCl2  also  has  somethin!  tc  ith 

whether  it  is  occluded  in  the  BaSC4  precipitate.  The  bos . pi  ; 
is  to  dilute  the  necessary  amount  of  BaCl2  to  ICC  . and  add  io 
lot  to  the  boiling  hot  solution  to  be  precipitate  J • i -•  c^itio, 
is  made  slowly,  with  stirring.  In  ordinary  routine  work,  however, 
it  should  be  satisfactory  in  most  cases  to  add  the  EaCl2  in  a 10# 
or  a 5a  solution,  being  careful  to  add  it  slowly  and  with  constant 
stirring  to  the  boiling  hot  solution. 


VII  MISCELLANEOUS  POINTS  IN  OIL  SULFUR  ANALYSIS. 

1-General . 

The  mo s t convenient  method  for  weigiiing  oil  samples  was 
found  to  be  a weighing  bottle  which  has  a medicine  dropper  ground 
into  a tight  joint  at  the  neck.  This  was  easy  to  handle,  and  pre- 
vented volatilization  of  the  oil. 


- 


(39) 

Reagents  should  be  the  best  obtainable,  and  laboratory 
fumes  should  be  carefully  excluded.  Blanks  should  always  be  run 
on  each  new  lot  of  reagents,  and  more  often  if  necessary,  as  im- 
purities crop  up  where  least  expected.  A case  in  point  during  the 
present  investigation  was  a fresh  bottle  of  Merkels  ’’pure'  BaC2, 
which  was  found  to  contain  a high  percent  of  S04~“> 

It  is  advisable  to  run  blanks  on  every  fresh  packet  of  fil- 
ters, by  selecting  about  four  from  different  parts  of  the  pack. 

It  was  found  in  practice  that  the  weight  of  the  incinerated  fil- 
ter which  had  been  treated  exactly  as  the  sample  was  always  higher 
than  that  given  on  the  label. 

For  routine  work  it  is  sometimes  convenient  to  use  Gooch 
crucibles,  but  they  have  to  be  carefully  filled  with  digested  and 
washed  asbestos  fiber.  It  is  easy  to  go  wrong  with  Gooch  crucibles 
in  ignition  work. 

In  igniting  the  precipitates  a blast  should  not  be  used,  for 
BaS04  decomposes  slowly  at  the  temperature  of  the  blast  lamp.  There 
is  also  danger  of  blowing  particles  of  PaSC4  out  of  the  crucible. 

R-Peroxide  Bomb. 

Attempts  to  guess  out  the  amounts  of  accelerator  reagents  to 
be  used  result  in  frequent  incomplete  fusions.  These  should  be 
weighed  with  fair  regard  for  accuracy.  For  speed  of  manipulation 
it  was  found  convenient  to  weigh  out  the  accelerator  in  doses, 
folding  the  doses  in  small  papers.  These  papers  of  doses  can  be 
bunched  into  packets,  and  are  then  in  convenient  form  to  add  imm- 
ediately witiiout  loss  of  time  during  the  runs. 


. 


•'31 


(40) 

In  precipitating  out  the  iron,  a good  excess  of  NH40H  should 
always  be  added,  or  else  some  of  the  sulfate  may  be  held  in  com- 
bination in  the  precipitate  as  basic  ferric  sulfate.  For  the  same 
reason,  the  solution  should  only  be  heated  enough  to  coagulate 
the  F e ( 0 H ) 3 sufficiently  for  good  filtration.  See  Treadwell-Hall 10 2 
The  Fe (OH) 3 precipitate  should  be  well  washed  with  hot  water, 
for  gelatinous  precipitates  are  notorious  for  retaining  soluble 
salts.  When  it  is  considered  that  it  takes  from  10  to  20  washings 
to  entirely  rid  the  PaS04  precipitate  from  chlorides,  it  does  not 
seem  reasonable  to  suppose  that  4 washings  of  the  Fe(0E)s  precip- 
itate are  sufficient,  as  stated  by  Franks. 


' 

, 


(41) 


TABLE  I 

Comparative  Results  By  Different  Methods-  Otsubo98 


Results  by 

the  methods  given: 

Oil 

Oxygen  Bomb 

Peroxide  Bomb 

Whi t tum-Otsubo 

Mex.  crude 

3.79  % S 

3.97  % S 

3.76  % S 

Light  oil 

0.587 

0.580 

0.528 

TABLE  II 

Comparative  Results  By  Different  Me thods-Vandaveer9 6 


Results  by  the 

methods  given: 

Oil 

Peroxide  Bomb 

Whi  t,  turn 

Ro the-Vandaveer 

Fuel  oil 

0.367 

0.33  1 

Fuel  oila 

0.340 

0.360 

0.408  • 

Kerosene  3 

0.037 

C.040 

Color  oil 

0, 295 

0. 2!  1 

Crude 

0.430 

0. 200 

Crude 

0.  200 

0.  187 

The 

only 

instances 

given  in 

frhich  results 

by  the  wet 

and 

dry 

combination 

methods 

were  not  lower 

than  in 

the 

bomb 

methods . 

MOTE:  Results  given  on  this  page  are  averaged  results  from 
the  references  cited. 


TABLE  III 

(42) 

Test  Funs  on  California  Crude  Oil 

Method  Percent  S. 

Peroxide  bomb  method;  samples 

Average  of 

_ - s amp 1 e s . 

about  .5  g.;  Duplicates  shown  0.998  % S 

checked  within  .015%  sulfur 

2 

Oxygen  bomb  method;  samples 

about  .9  g.;  individuals,  1.003 

.988%,  1.028%,  .993%  S 

r? 

u 

AMOUNT  OF  SULFUR  IN  CALIFORNIA  CRUDE  taken  to 

TABLE  IV 

be  1.000 

per  cent. 

Experimental  runs  on  California  crude. 

Method. 

Percent 

Samples 

Whittum,  anhydrous  MgCl2  in  dish  with  oil 

0.328% 

2 

Whittum,  but  Se0Cl2  the  oxidizing  agent 

0.278 

O 

Whittum,  but  SeCCl2  the  oxidizing  agent 

0 . 290 

2 

Whitt um,  Eschka  directly  after  fuming  nitric 

0.684 

2 

Whittum,  oil  diluted  with  benzene 

0.  727 

2 

Whittum  + 10  cc.  CC14 

0.758 

2 

Whittum  + 15  cc.  CC14 

0.  768 

2 

4^ 

CO 

) 

TABLE  IV  (continued) 

Method 

Percent  S 

Samp les 

Whittum,  CCi4  and  7 cc.  fuming  nitric  acid 

0.  734 

2 

Whittum,  CC14  + 7 cc.  fuming  nitric  + 2 g.  MgO 

+ 4 g,  Na2C03 

0.8  13 

2 

Same  as  previous,  except  12  cc.  fum.  nitric 

0. 749 

2 

Whittum,  large  amt.  Eschka  heaped  over  dish 

1 . 108 

! 

Average  by  the  selenium  oxychloride 

0.284 

4 

Average  most  representative  Whittums 

0. 734 

10 

TABLE  V 

California  crude  by  the  Ro the  method. 

Method 

Percent  S 

Samples 

Without  modification^ 

0.685 

1 

T.  enty  cc.  CC14  added,  before  the  fuming  nitric 

0.782 

1 

Same  as  previous 

0.75  ! 

1 

Same  as  previous 

0.786 

! 

Same  as  previous 

C.  686 

1 

Representative  average 

C.  773 

3 

a 

Five  hundred  cc.  flasks  were  used  in  all 

exp  er iments 

with  the  Rothe  method. 

. 


(44) 


TABLE  VI 


Open  fusion  experiments  with  the  California  crude. 

Method  Percent  S Samples 

10  g.  Ca02  + 3 g.  oil  0.383  2 

20  g.  CaO 2 + 1.5  g.  oil  0.579  2 

lOg.  Ca02+6g.  Ba02+2g.  oil  0.412  2 

10  g.  CaC 2 ( fresh)  + 3 g.  Ma2CC2  + 1.5  g.  oil  0.650  2 

5 g.  CaO 2 (fresh)  + 4 g.  Pa2CC£  + 1.5  g.  oil  C.54!  2 

TAPLE  VII 

Comparative  runs  on  Mexican  crude. 

Method  Percent  S Samples 

Peroxide  bomb  4.940  2 

Eothe  1.670  2 


(45) 


VTIJ  SUMMARY  AND  CONCLUSIONS. 

1.  A review  has  been  made  of  the  various  methods  which  have 
been  proposed  for  the  analysis  of  sulfur  in  petroleum  oils  or 
similar  substances. 

2.  Methods  where  the  oil  is  fused  in  open  dishes  with  alkalis 
or  mixtures  of  alkalis  and  oxidizing  agents  are  held  to  be  inacc- 
urate, due  to  loss  of  sulfur.  Efforts  to  modify  the  general  pro- 
cedure, together  with  the  trial  of  new  oxidizing  agents  to  pre- 
vent such  loss  of  sulfur,  have  not  met  with  success. 

3.  The  Whittum  and  Rothe  methods,  whereby  the  oil  is  treated 
with  liquid  oxidizing  agents,  followed  by  dry  fusion  of  the  resi- 
due, were  also  tried  out  with  crude  oils.  Loss  of  sulfur  was  found 
in  every  case,  and  efforts  to  modify  the  methods  were  unsuccess- 
ful in  preventing  such  loss. 

4.  It  was  demonstrated  that  loss  of  sulfur,  as  shown  under  2 
and  3,  is  occasioned  at  two  points:  (a)  loss  by  volatilization  of 
the  oil  in  the  preliminary  stage;  and  (b)  loss  by  reduction  or 
otherwise  in  the  burning  off  of  the  residue. 

5.  Addition  of  an  inert  solvent  to  the  oil  before  treatment 
(by  wet  oxidizing  agents)  does  not  diminish  the  efficiency  of  the 
oxidation,  and  has  the  advantage  of  preventing  loss  of  sample 
occasioned  by  too  violent  a reaction. 

6.  Good  results  have  been  claimed  for  the  Whittum,  Waters, 
and  Rothe  methods  when  used  on  low  sulfur  fractions,  but  in  view 
of  the  inaccuracies  found  in  the  Whittum  and  Rothe  methods  as 
applied  to  crude  oils,  there  is  also  reason  to  doubt  the  accuracy 


(46) 


of  such  procedures  with  low  sulfur  oils. 

7.  As  far  as  the  present  work  would  show,  the  only  practical 
methods  of  sulfur  analysis  which  can  be  viewed  with  entire  con- 
fidence are  the  oxygen  bomb  and  the  sodium  peroxide  bomb  methods, 
which  can  be  applied  to  medium  or  high  sulfur  oils;  and  the  lamp 
method,  which  is  resorted  to  with  very  low  sulfur  oils.  The  Carius 
method  and  the  combustion  tube  method,  although  accurate,  are  not 
held  to  be  generally  applicable.  The  Meulen  reduction  method  is 
subject  to  the  same  objection. 

8.  It  is  shown  that  too'much  barium  chloride  solution  is  fre- 
quently added,  to  obtain  the  best  results. 

9.  Miscellaneous  points  are  given  in  connection  with  oil  sul- 
fur analysis. 

10.  Tables  of  data  are  given  showing  analyses  of  oils  by  diff- 
erent methods. 


IX  BIBLIOGRAPHY 


(47) 


1.  Peckham,  Proc.  Am.  Phil.  Soc.  £6  108  (1897).  Petroleum  and 

Its  Products  i 296.  Kissling,  Chem.  Zeit.,  2£  499  (1902). 
Richardson  and  V, 'all ace,  Eng.  Min.  J . , 78  359  (1902). 

Rogers,  Trans.  Am.  Inst,  Min.  Eng.,  52  969  (1917).  Schwartz 
and  Nevitt,  Petroleum  7 No  s,  2,  23,  96,  98,  100,  102  (1919). 

2.  Clarke,  Data  of  Geochemistry  727  (1920). 

3.  Mabery,  Proc.  Am.  Acad.  Arts,  Sc.,  31  17,  43  (1694). 
Richardson  and  Wallace,  J.  Soc.  Chem.  Ind.,  20  690  (1901). 
Waters,  Sulphur  in  Petroleum  Oils,  U.  S.  Bureau  of  Standards 
Technologic  Paper  No.  177,  page  5 (1920). 

4.  Girard,  Petroleum  2 No.  3 (1906).  Scheibler,  Der,  46  1815- 

26  (1915);  c.  A.,  1C  840  (1916);  *'  ters.  Standards  Paper- 
177  P . E (1920) . 

5.  Mabery,  J.  Soc.  Chem.  Ind.,  19  ECS  (1900);  Mabery  and  Cuayle, 

Proc.  Am.  Acad,  Arts  Sc.,  41  89  (1905). 

6.  Second  reference  under  5;  Ellerton,  J,  Soc.  Cehm.  Ind., 

31  10-12  (1912);  Waters,  Standards  Paper  177  p . 6. 

7.  Waters,  Standards  Paper  177  p.  6. 

8.  Chem.  Zeit.,  21  203  (1897);  Waters,  Standards  Paper  177  p.  6. 

S.  Veith,  Dingl . pol.  J.  , 277  £67  (1-890);  Waters,  Standards 

Paper  177  p.  6. 

10.  J.  Ind.  Eng.  Chem.,  9 479  (1917);  Waters,  Standards  Paper 

177  p - 6. 

11.  Waters,  Standards  Paper  177  p.  6. 

12.  Z.  angew.  Chem.,  ie  1529  (1905). 


(48) 


13.  Waters,  Standards  Paper  177  p . 5, 

14.  Waters,  Standards  Paper  177  p.  ie. 

15.  Pecueil,  41  112-120  (1922). 

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